The Research Of Biodiesel Production With Solid Base Catalyst By Using Waste Frying Oil

The conflict of the increasing demand for energy and the limited fossil resourcesin the worldwide, as well as the necessity of environmental protection enforce humanto develop friendship and reproducible energy. Fatty acid methyl ester（FAME）,which is also knwon as biodiesel, is produced by the transesterificationreaction between plant oil/animal fat and methanol or other alcohols. As typical"green energy", biodiesel possesses advantages such as low sulfur content, lessemission of sulfur dioxide, sulfur and other harmful gases in the combustion process,rich raw material sources and high renewable, which make biodiesel an idealalternative fuel for petroleum diesel. In this thesis, different types of solid base weresynthesized and then used to catalyze waste frying oil （WFO） for the preparation ofbiodiesel. Pretreatment process of feedstock WFO, synthesis and characterization ofcatalysts as well as the leaching of catalyst active components were studied. Mainresearch results are as follows:（1） The feedstock WFO was purified. WFO which generated in the foodprocessing has complex compositions and high levels of free fatty acid. WFO needsdegumming, deacidifying, and bleaching because the acid value of different batcheswere in the range of1.200¹.900mgKOH g^-1（oil）. After purification, the acid valueof purified WFO was in the range of0.256⁰.874mgKOH g^-1（oil）, the saponificationvalue was in the range of196.8¹98.7mgKOH g^-1（oil）, and the average molecularweight was in the range of848.5⁸59.0g mol^-1. These parameters meet standards offeedstock oil for biodiesel production.（2） Different types of calcium base catalysts were synthesized and the catalyticactivities were compared in biodiesel production by using WFO. Firstly, CaCO₃microsphere was synthesized by the solution precipitation method and then calcinedto produce calcium-based catalyst precursor. Then, KF/CaO, CaO-Al₂O₃,CaO-diatomite and CaO-MgO solid base catalyst were prepared by several methods including grinding method, coprecipitation and equal volume impregnation andfurther applied for the preparation of biodiesel. The results showed that CaO-Al₂O₃（4.5:1） obtained by grinding method has the best catalyst effect. Under theconventional conditions （n（methanol）: n（oil）=9:1, catalyst total content=3%,reaction time=40⁶0min, reaction temperature=65℃, m（N-hexane）: m（oil）=0.6）,the transesterification yield reached to above98%. The proposed catalyst alsopossesses high stability, and it can be reused for70times in transesterificationreactions without any treatment. SEM and BET results showed that the structure ofthe catalyst is porous and reticular and the specific surface area is15.971m2g^-1, XRDspectra revealed that a new crystalline phase Ca12Al14O33appeared as a result of CaOand Al₂O₃bonding.（3） The quality cretieria of the prepared biodiesel are basically up to theBlending （B5） of Biodiesel Fuel National Standards （GB/T25199-2010）. Theproduction was detected according to the GB/T25199-2010, the results showed thatthe density of the prepared biodiesel in this experiment is880kg·m^-3, the cold filterplugging point is3℃, the closed flash point is80℃, the kinematic viscosity is6.790mm2·s^-1（20℃） and the cetane number is45, all the indicators tested are in line withthe standard. In addition, the calcium leaching from solid phase catalyst was inspectedby ICP-AES for the investigation of the Al₂O₃carrier effect, which turned out to bethat although the catalystic efficiency of CaO-Al₂O₃was much higher than that ofCaO alone, the addition of Al₂O₃did not prevent the calcium leaching.